The event in The Domain, which attracted fewer than 100 of the 5000 people who had registered to attend, came to nothing as police ordered protesters to disperse 15 minutes before it was scheduled to begin on Tuesday.

Hundreds of police - including officers from the public order and riot squad - were deployed at the park and six arrests were made.

Five of those people - three men and two women - were handed $1000 fines for breaching public health orders, while a third woman was handed an infringement notice for offensive language.

"We appreciate people's right to protest," NSW Police Assistant Commissioner Mick Willing told reporters.

"We understand the issues that are in question here are significant and are sensitive to a lot of people. However we must do what we can to ensure the public, in general, are safe."

Rally organiser Paddy Gibson was one of those arrested.

He said supporters were asked to gather in groups of fewer than 20 after failing on Monday to overturn a NSW Supreme Court decision prohibiting the protest.

Mr Gibson, who was ushered into NSW Parliament by Greens MP Jenny Leong after being released, said he'd been told by police that despite the park's size, only 20 protesters would be permitted.

"We weren't allowed to give it a run even though Westfield is allowed, as well as the casino and the NRL," the 37-year-old told AAP.

"People are allowed to come together to make profits but they're not allowed to come together to say black lives matter; that's a disgraceful situation in NSW."

Another attendee who was arrested, Bundjalung woman Vanessa Turnbull-Roberts, said all protesters had complied with COVID safety regulations.

"Police were the only threat ... a national disgrace and abuse of power," Ms Turnbull-Roberts posted on Twitter.

A petition with 100,000 signatures was later delivered to parliament calling for justice for Indigenous man David Dungay Jr.

Mr Dungay, 26, and a diabetic, died in December 2015 after five prison officers stormed his Sydney jail cell to stop him eating biscuits.

The Dunghutti man's mother, Leetona Dungay, thanked attendees for their support of her family.

His nephew, Paul Silva, said handing over the petition was "amazing" but "just one step forward".

"It's very important for our family that we get justice for David Dungay Jr and that there are systematic changes in jails," Mr Silva told reporters.

"I never really recognised Aboriginal deaths in custody until it happened to our family. I wish it upon no one."

Justice Mark Ierace on Sunday accepted the possibility of community COVID-19 transmission at the rally made the event too risky.

The appeal court on Monday dismissed a challenge to Justice Ierace's decision.

NSW Premier Gladys Berejiklian had earlier on Tuesday appealed to "people's conscience and ethical standards" not to attend.

Black Lives Matter rallies have been held around the globe, sparked by the murder of US man George Floyd by police in Minneapolis on May 25.

Australian Associated Press